I have an old ipad. What I would like is for it to be a simple juke box connected to my computer/computer speakers. I just want to do it via the old ipad usb connector. Is there a simple way to do this?

There are multiple ways to do this, works best if you have WiFi as it eliminates the wired tether to the computer.

Option 1 requires the USB connection but no computer or WiFi
Option 2 requires a computer and WIFi but no usb. If you want to play content on the computer, see if the second option below works.
Option 3 requires WiFi but does not need a computer or USB connection

This allows you to playback music on a computer, requires WiFi for connection

3)Airplay, this is built into the iPad, you will need WiFi and one of the following, Airplay Compatible speaker, AppleTV, Airport Express, or Airplay AV receiver (Onkyo, Denon, Marantz etc) that supports the Airplay protocol or
make an Airplay receiver using the PC + WMC but it is quite involved.

The Airport Express has spdif digital output that can be sent to an AV receiver/processor

This allows you to play the content on the iPad. You might be able to stream it from a shared folder on another machine although I have not tried it.http://support.apple.com/kb/ht4437

As you have a older iPad, check to see if you iPad can runs IOS v5 or later